natural or synthetic nuclei?

[David65]

Hi all
I'm new here so I apologise if this is a silly question.
what are the differences between natural and synthetic nuclei for culturing pearls, are there clear benefits of using one over the other? or is it simply a personal preference? from what I've read there seems to be a preference towards natural nacre nuclei.
Why dont people just use synthetic nacre? it seems like it would be cheaper and less labour intensive to synthetically produce the nuclei rather than machine them from shell... but obviously I'm missing something?

 

[jshepherd]

The density and the thermal coeffecient of expansion need to be a good match for the nacre that develops around the bead. Otherwise the pearl will likely crack when heated (drilling).

 

[Cyril Roger Brossard]

As explained by Mr. Shepherd, density would be the most important, especially for the market value of said pearl.

 

[Daddys Little Pearl]

And having no knowledge on this at all, but a thought that the poor little creature might be much happier having something small inserted that at least it might recognize genetically instead of a larger round ball of mother of pearl or other substance. Not that it is going to be happy with any unplanned surgery in the first place. This might be another thread, do oysters etc have feelings? Sorry, this is what my brain does with lack of sleep.

 

[Pearl Dreams]

They have no brain, and without a brain there can be no consciousness-- hence, I would think, no suffering.

Their bodies deal with physical irritants by secreting nacre to protect the delicate tissues from damage, but that does not mean they experience pain-- or happiness. I would think one needs a brain for that.

 

[Daddys Little Pearl]

Ok Pearl Dreams, granted no brain, but something definitely controls their behaviour that at least resembles a "feeling", such as how they will close their shells or open depending on environment, etc. For instance when they are removed from the water and set a while, they do react to their environment whether it be temperature, lack of water, etc. So with no brain,what controls all this? Yes MY brain woke up and now I am really curious as to how these little fellows ( so beloved to all us pearl lovers ) function and react. If their body is reacting for instance when it secretes the precious nacre, something has to control that function. They have a mouth of sorts, how to they know what to eat? And they have sex or at least they reproduce, what controls that?

 

[Cyril Roger Brossard]

No, the 'brain' of a mollusk is a nervous system divided into a pedal ganglia near base of foot, a cerebral ganglia near the oesophagus and a visceral ganglia near adductor muscle.
centralized or autonomic or peripheral nervous systems are found in many creatures, this doesn't not imply capability to analyze stimulus in a conscious manner.
Feelings and emotions are more a psychological or philosophical approach than a biologic one.

"There is no major control center (brain), and in this sense the nervous system is decentralized." APATHY,STEFAN (1897)

 

[Daddys Little Pearl]

Thanks Cyril,biology/science was not one of my favorites in school. So why then do they anesthesize the oysters, I thought anesthetic only acts on a brain?

 

[Cyril Roger Brossard]

Thanks Cyril,biology/science was not one of my favorites in school. So why then do they anesthesize the oysters, I thought anesthetic only acts on a brain?

most welcome.

Anaesthesia acts on the muscle and on the nerves.
Anaesthesia inhibits the transmission of influx in the nervous system...

 

[Daddys Little Pearl]

Thanks Cyril, very interesting little creatures, these pearl producers. Sorry if I hijacked this thread a little towards the science, but this is what I love about this forum, there is so much knowledge to share with others.

 

[Lagoon Island Pearls]

So with no brain,what controls all this?

Hormones.

They have a mouth of sorts, how do they know what to eat?

Mollusks without siphons are called lamellibranchs, which have gills that consist of long, folded filaments with cilia at the end that draw in water for respiration and also filter food particles. Temperature dictates the size of cells they can digest, where they can eat larger cells in warmer months and only smaller in cold.

And they have sex or at least they reproduce, what controls that?

Shellfish go into $exual maturity annually and when they become so engorged, virtually any event can trigger it. The sheer volume of spawning animals in a single area will invariably lead to fertilization.

 

[pearlescence]

Ohhhhhhhhhhh Dave..it's a long time since I've seen the word lamellibranch - O level geology classes with Mr Bacon x years ago!
I'll see your lamellibranches and raise you two cephalipods and a gastropod ! HA!

 

[Lagoon Island Pearls]

Sorry if I hijacked this thread a little towards the science, but this is what I love about this forum, there is so much knowledge to share with others.

Those were good questions. Sometimes, it's important to have clarity on some basic points to understand something more complex.

Their bodies deal with physical irritants by secreting nacre to protect the delicate tissues from damage, but that does not mean they experience pain-- or happiness. I would think one needs a brain for that.

Shellfish have reflexes, but not pain as we know it.

The first part of your point is worth commenting to the topic. A point often missed, the opposite is also true. Shellfish have the ability errode shell with acids every bit as easily as the ability to build shell with bases. No more is this apparent than when a mollusk repairs a broken shell. So complexed are the epithelial cells, they are able to perform one function or the other, in adjacent cells. It's particularily ongoing in scallops normally, which gives rise to the commonly "dimpled" textures in both pearls and shells. Mussel shells are like razor blades when cracked. Attempting to mineralize an "irritant" such as this, would likely exacerbate the injury because of the close proximity of the cells, whereas backing off a bit, then applying acid will wear down the sharp surface.

Ocean salinity is not constant. In fact, (especially in the temperate zones) it's up and down the scale, sometimes with extremes with rains and floods. All living things need calcium and if they cannot get it from food they take it from shells or bones. Even at best, it's always a balance of a two way street.

Jeremy made an very important point from a commercial standpoint, while from a biological position, the ideal nucleus is one that behaves as biologicals behave. One might argue that plastic gets used for mabes (extrapallial pearls) all the time and opals and mud have been successfully used as nuclei for gonadal pearls, but they are far from ideal.

I suppose a matrix of calcium carbonate, aragonite... possibly vaterite might do well to form beads of correct hardness and surface tension, but then it becomes an issue of viability.

Last report is there remains a glut on American mussel shells and the need to look to a synthetic alternative isn't all that important at this time.

 

[Cyril Roger Brossard]

Hormones.

mmmh, purely an academic question, as I am not a specialist in this area, could you please tell us if those hormones are the result of an endogenous biosynthesis or picked up from the environment?(i.e. progesterone, testosterone and 17β-estradiol)

Thank you.

 

[jshepherd]

Their bodies deal with physical irritants by secreting nacre to protect the delicate tissues from damage ...

This is what is often taught, but is not correct either. It lends to the grain-of-sand myth.

 

[Daddys Little Pearl]

Ok I have spent a lot of time googling the web on this issue, and here are my humble conclusions: Do the have a brain, NO. period, everyone agrees on this part. Do they feel pain? NO probably not, although no one can say they really know for certain. I'll go with NO on this one also. But do they "Feel" things, there seems to be a strong consensus of Yes to that one. And from what I can find, anaesthesic works on nerve endings to block sensations, but does not relax a muscle. Several food sites say that dropping lemon juice on a live oyster provokes a response, in other words they do "feel" sensations so some extent. In other words they do have "feelings" , not emotional, but physical feeling. So getting back to the OP question, this would I think reinforce why it would be best to use tissue nucleation or other natural substances instead or large or man made objects if for no other reason than to cause less disturbance to the oysters operating system, whatever it may be. Possibly the use of such objects might have been one of the causes for so many oysters demise in the early days of pearl culture (along with pollution, infection, etc of course). Just a thought. This has been very interesting. Thanks to the original poster for providing such food for thought. ( I forgot to mention I am a vegetarian, and even when I used to eat meat and fish, I have never been in the presence of an opened live oyster. )

 

[Pearl Dreams]

But I thought if a parasite entered (not a grain of sand), that triggered nacre production?

 

[Daddys Little Pearl]

Wow Pearl Dreams, I forgot that important point, the oyster has to "feel" the intruder to trigger the production of nacre!

 

[Lindaphillipsbong]

I would imagine that "pain" or some such thing might be one of the first neural sensations to evolve .... causing withdrawal or "running away", protecting the organism from dangerous stuff. I'll bet our beloved oysters feel some type of mild irritation in the very least when we open the doors and poke their private parts.
Linda.

 

[Lagoon Island Pearls]

mmmh, purely an academic question, as I am not a specialist in this area, could you please tell us if those hormones are the result of an endogenous biosynthesis or picked up from the environment?(i.e. progesterone, testosterone and 17β-estradiol)

Thank you.

That's a serious question. I'm no specialist in that area either, but it always comes up in the differential diagnosis. In the absence evidence by instrumentation, I take a lot of guesses. It usually comes into question during the septic/aseptic discussion. The ratio of non-sterile to sterile is definitely higher in extrapallial pearls. Even in cases of spontaneously formed, sterile, auto-immune pearls an environmental factor may be implicated. I find it safer to stick to "multiple etiological factors".

Whether something beneficial is aquired while a mollusk is otherwise under a environmental stress will always remain a valid question. I've certainly seen a few cases where invasive species were highly beneficial. (though I'm speaking biomass as opposed to a single specimen) Yet any mollusk in the absence of pearls or other malady are remarkably self-regulatory but greatly influenced by lunar cycles (tides/quiescence) and seasonal temperatures. Those would be major environmental factors affecting internal mechanisms.

It doesn't take much to induce mollusks to spawn. At least not around here, anyway. Often, simply putting them back in the water after transport has them giving up the gametes. Sinking them in water 10 degrees colder will too, though that might be hard in the tropics.

I wouldn't dismiss pheromones (sp) on reproductivity, but don't see much of a connection to shell building or pearls.

I'm a little over my head myself on the topic too.